Elevator systems typically include an elevator car that is supported for movement within a hoistway. The elevator car travels between different levels of a building, for example, to transport passengers, cargo or both to desired destinations. An elevator machine causes the desired movement of the car.
Many elevator machines include a motor that rotates a traction sheave to cause movement of a roping arrangement (e.g., round ropes or flat belts) from which the elevator car is suspended. The machine includes a drive that provides power and control signals to the motor to achieve the desired elevator car movement.
Typical arrangements include separated motors and drives. Hardwired connections between them facilitate achieving the desired motor operation based upon the control signals provided by the drive. One issue with traditional arrangements is that the amount of wiring required between the drive and the motor introduces additional expense and complexity when installing or repairing an elevator machine. Another issue that is common to most drives is that some arrangement must be provided for cooling the electronics of the drive.
One attempt at changing an elevator drive arrangement is shown in WO 2005/040024. That document describes a proposed separation of drive components with an inverter integrated with a motor.
The increasing market demand for lower cost, high space utilization, energy efficiency, and low noise environment of modern buildings translates into miniaturization and high power density, low noise and energy efficiency requirements for elevators, their motors and their electronic drives. One of the key factors determining acceptable power density in the motor and in the drive is the thermal management or cooling system.
The cooling system of the motor is typically based on heat removal through the natural convection to surrounding air from the surface of the motor, which in many cases determines the motor size. Modern elevators usually employ permanent magnet motors with a brushless rotor so that only the stator has a winding. Resistive losses present the source of heat that needs to be removed. The typical brake in an elevator system also has at least one electromagnetic coil with associated resistive losses, and often represents the second largest heat source in the system. Additionally, the efficiency of bearings is limited by mechanical friction and aerodynamic and hydrodynamic drag, and thus the bearings contribute additional heat to the machine.
Motor drive cooling systems usually include fans for forced air circulation and removal of the heat that results primarily from power dissipation of power electronic components. The heat sources are connected to a heat sink and fans are forced air circulation is used to move heat from the heat sink to the ambient environment. Typically heat sinks are costly and take up significant space. Fans contribute to noise, reduce drive reliability and increase maintenance costs. It is desirable, therefore, to eliminate fans or, at least, reduce the size or number of fans. An alternative to using fans has been to provide an extended surface inside or outside of the drive enclosure and use natural convection mechanisms.
Liquid cooling, though not as common as direct forced air cooling, is also applied in some cases to power electronics. In such a system, the high heat flux of the power electronics components is absorbed by a moving liquid and carried to a remote liquid-to-air heat exchanger. While liquid cooling systems can provide for a more compact power electronics section, the size of a remote heat exchange must be similar or even larger than required by a forced air flow system.
An exemplary elevator machine includes a motor having a case. A drive provides power and control signals to the motor. The drive is supported adjacent the motor case such that the drive and the motor are at the same location.